Modeling and experimental validation of a triple-screw pump for internal combustion engine cooling

Abstract

• Development of the mathematical model of a triple-screw pump. • Idler screws without a dedicated support determine complex friction phenomena. • Experimental assessment of volumetric and mechanical performances. • Maximum global efficiency achieved equal to 70% • 8.2% efficiency improvement on ICE cooling application compared to centrifugal pump. Internal Combustion Engine (ICE) cooling system is receiving a new technological interest for the influence it has on primary harmful and CO2 emissions reduction. Improvements on pump efficiency are requested to reduce its required energy during real on-the-road operation. Present technology always considers centrifugal pumps whose efficiency is highly dependent on rotational speed: consequently, pumps designed to have a very high efficiency at design point, show poor performances during usual operation, wasting energy. This study aims to assess the screws pumps potentiality to substitute the traditional centrifugal pumps for engine cooling. The main advantage is that positive displacement pumps have an efficiency ideally non-dependent on rotational speed, flow rate and head delivered, so having requirements that can fit more the engine cooling features. A novel comprehensive zero-dimensional mathematical model has been formulated to predict the performances of triple-screw pumps, in terms of volumetric, indicated and mechanical efficiency as a function of main operating conditions of the pump. A wide experimental activity has been done, resulting in a good agreement with predictions in spite of the manufacture of the pump, which privileges a low-cost solution as it is requested for the specific sectors of application. The model, once experimentally validated, demonstrates a high validity as virtual platform for a model-based design, thus offering the possibility to include design aspects particularly suitable for engine cooling systems. At last, by simulating the World Harmonized Transient Cycle on an F1C IVECO 3l engine, the triple-screw pump shows an average efficiency about 8% greater than that of the centrifugal pump, leading to an energy saving equal to 18.5%. This result leads the way to the use of screws pumps also in the engine cooling system of an on-the-road vehicle, which could represent a new potential application, never considered before.